Thermally curable, thixotropic blends containing carbamate and/or allophanate groups

ABSTRACT

Heat-curable thixotropic mixtures containing carbamate and/or allophanate groups, comprising  
     (A) at least one oligomer and/or polymer selected from the group consisting of oligomers and polymers containing allophanate groups, carbamate groups, and carbamate and allophanate groups, and  
     (B) at least one thixotropic agent selected from the group consisting of urea derivatives preparable by reacting at least one amine and/or water with at least one isocyanate in the presence of at least one amino resin;  
     processes for preparing the mixtures, and their use as coating materials, adhesives and sealing compounds.

[0001] The invention relates to novel heat-curable thixotropic mixturescontaining carbamate and/or allophanate groups. The present inventionfurther relates to processes for preparing the novel heat-curablethixotropic mixtures containing carbamate and/or allophanate groups. Thepresent invention relates additionally to the use of the novelheat-curable thixotropic mixtures containing carbamate and/orallophanate groups as coating materials, adhesives and sealingcompounds. The present invention relates in particular to the use of thenovel heat-curable thixotropic coating materials containing carbamateand/or allophanate groups as clearcoat material, especially forproducing clearcoats as part of multicoat color and/or effect coatingsystems.

[0002] Thixotropic materials and coating materials comprising them havebeen known for a long time.

[0003] The use of thixotropic agents in coating materials is intended,inter alia, to allow comparatively thick paint films to be appliedwithout disruptive running. Especially in the case of nonaqueous coatingmaterials comprising a thixotropic agent based on urea derivatives, andat least at high solids contents, the resulting film surfaces areunsatisfactory in terms of their visual appearance (especially levelingand gloss) and, moreover, lead to coatings lacking “condensationresistance” (exhibiting blushing owing to water infiltration).Thixotropic agents based on silicas give coating materials which arelikewise unsatisfactory in terms of leveling.

[0004] A key feature of thixotropic agents is that the viscosity of acoating material prepared using them depends on the flow history and/orthat the thixotropic agents are pseudoplastic, i.e., the viscosity ofthe coating material decreases as the applied shear stress goes up.Starting from a baseline viscosity, the viscosity decreases under shearstress and returns only gradually to the initial level after the shearstress has been removed. A thixotropic gel, for example, liquefies as aresult of input of mechanical energy (stirring or the like) andsolidifies again only gradually after the end of the input of energy.Pseudoplastic or thixotropic properties are advantageous for paintprocessing. In particular, the tendency of a coating material to run onapplication at high wet-film thickness may be controlled and reduced. Onthe other hand, thixotropic agents must not adversely affect the opticaland chemical properties of a finished coating produced using them. As ageneral rule, thixotropic agents are particulate and are present indispersion in a coating material, whether aqueous or nonaqueous. In thecase of the urea derivatives, these thixotropic agents are acicularcrystals, in part with a helical twist, for which, preferably, aparticle size distribution between 0.1 μm and 6 μm (95-99% of theparticles, based on the volume) is established and 80% of the crystals(based on the number) are smaller than 2 μm.

[0005] Coating materials comprising constituents containing allophanategroups are known from the German patent application DE 198 39 453 A1.These coating materials are capable of wide application and areoutstandingly suitable for the wet-on-wet technique for producingmulticoat color and/or effect coating systems. The coatings producedfrom the coating materials are highly compatible with other coatings andare scratch-resistant and weathering-stable. Providing these knowncoating materials with thixotropic agents is not described in the Germanapplication.

[0006] The international patent application WO 00/31194 disclosesthixotropic agents comprising urea derivatives and polymers containinglateral or terminal carbamate groups. The urea derivatives may beprepared by reacting monoamines with polyisocyanates in the presence ofthese polymers. The coating materials provided with the thixotropicagents may also comprise surface-active or interface-active substances(surfactants; cf. Römpp Lexikon Lacke und Druckfarben, Georg ThiemeVerlag, Stuttgart, New York, page 271, “Surface-active substances”).According to example 1, page 23 line 22, of the international patentapplication, a silicone-glycol copolymer (Worlee® 315) is used. Thethixotropic agents improve the thixotropic behavior of the coatingmaterials provided with them and effectively suppress the tendency torun. The coatings produced from them exhibit high gloss and a high levelof hardness.

[0007] The German patent application DE 199 46 048 A1 discloses coatingmaterials whose binder comprises at least one resin containing lateraland/or terminal carbamate groups and preparable by reacting a resincontaining at least one hydroxyl group with phosgene to give a resincontaining at least one chloroformate group, which resin is then reactedwith ammonia, primary amines and/or secondary amines. Apart from thecustomary and known crosslinking agents for heat curing, the coatingmaterials may further comprise numerous different additives. Forinstance, besides numerous other additives, mention is made of sagcontrol agents (thixotropic agents), such as ureas and/or modified ureasor silicas, as described for example in the aforementioned literaturereferences EP 0 192 304 A1, DE 23 59 923 A1, DE 18 05 693 A1, WO94/22968, DE 27 51 761 C2, WO 97/12945 and farbe+lack, 11/1992, pages829 ff. Precise details as to the amounts in which these additives areto be used are lacking. It is merely stated that the additives are addedin customary and known, effective amounts, which depending on theadditive are from 0.001 to 500 parts by weight per 100 parts by weightof resin and crosslinking agents. In the examples, however, theseadditives are not used.

[0008] The known coating materials have numerous advantages which,however, can be attributed to the specific binders or resins containingcarbamate groups.

[0009] The international patent application WO 00/37520 discloses ureaderivatives preparable by reacting at least one amine with at least onepolyisocyanate in the presence of at least one amino resin, asthixotropic agents. The thixotropic agents are intended to be capable ofbeing employed universally. Their use in heat-curable thixotropicmixtures containing carbamate and/or allophanate groups is not describedin the international patent application. Nor does the patent applicationreveal whether—and if so to what extent—the thixotropic agents influencethe scratch resistance of coatings, adhesive films and seals producedfrom the thixotropic coating materials, adhesives and sealing compoundsin question.

[0010] The heat-curable thixotropic coating materials, adhesives andsealing compounds containing carbamate groups which are known to date,especially the clearcoat materials, therefore have a number of technicaladvantages, which ought to be retained in the course of their furtherdevelopment. Despite the high technological level attained, thecoatings, adhesive films and seals produced from the heat-curablethixotropic coating materials, adhesives and sealing compoundscontaining carbamate groups which are known to date still leavesomething to be desired in terms of their scratch resistance and reflowcharacteristics.

[0011] It is an object of the present invention to provide novelheat-curable thixotropic mixtures containing carbamate and/orallophanate groups that are suitable for use as coating materials,adhesives and sealing compounds, these compositions attaining the hightechnological level of the prior art, if not indeed exceeding it.Furthermore, the novel heat-curable thixotropic coating materials,adhesives and sealing compounds containing carbamate and/or allophanategroups should give coatings, adhesive films and seals which attain thehigh technological level of the prior art, if not indeed exceed it, andat the same time possess high scratch resistance and very good reflowcharacteristics.

[0012] The invention accordingly provides the novel heat-curablethixotropic mixtures containing carbamate and/or allophanate groups,comprising

[0013] (A) at least one oligomer and/or polymer selected from the groupconsisting of oligomers and polymers containing allophanate groups,carbamate groups, and carbamate and allophanate groups, and

[0014] (B) at least one thixotropic agent selected from the groupconsisting of urea derivatives preparable by reacting at least one amineand/or water with at least one isocyanate in the presence of at leastone amino resin.

[0015] In the text below, the novel heat-curable thixotropic mixturescontaining carbamate and/or allophanate groups are referred to as the“mixtures of the invention”.

[0016] Further subject matter, processes and uses in accordance with theinvention will emerge from the description.

[0017] In the light of the prior art it was surprising and unforeseeablefor the skilled worker that the object on which the present inventionwas based might be achieved by means of the mixtures of the invention. Aparticular surprise was that the coatings, adhesive films and sealsproduced from the mixtures of the invention, especially the coatings,combine a high level of hardness with high scratch resistance and verygood reflow characteristics, since hardness and scratch resistance arefrequently contradictory parameters.

[0018] Here and below, polymers are understood to be substancescontaining on average per molecule at least 10 monomer units. Oligomersare understood to be substances containing on average per molecule from3 to 15 monomer units. For further details of these terms, refer toRömpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, NewYork, 1998, “Oligomers”, page 425.

[0019] In a first variant in accordance with the invention, the mixturesof the invention comprise at least one oligomer and/or polymer (A)selected from the group consisting of oligomers and polymers containingallophanate groups or allophanate groups and carbamate groups.

[0020] It is preferred to use oligomers and/or polymers (A) containingon average per molecule at least one allophanate group and preferably atleast two, with particular preference at least three, and in particularat least four, allophanate groups.

[0021] It is likewise preferred to use oligomers and/or polymers (A)containing on average per molecule at least one allophanate group and atleast one carbamate group and also, preferably, at least two, withparticular preference at least three, and in particular at least four,allophanate groups and at least one carbamate group, in particular atleast two carbamate groups.

[0022] The oligomers and/or polymers (A) containing carbamate groupscontain on average per molecule preferably at least one carbamate groupand more preferably at least two, with particular preference at leastthree, and in particular at least four, carbamate groups.

[0023] The mixtures of the invention comprise at least one thixotropicagent (B) selected from the group consisting of urea derivativespreparable by reacting at least one amine with at least one isocyanatein the presence of amino resins.

[0024] Furthermore, the mixtures of the invention may comprise at leastone, especially one, silica as thixotropic agent (C).

[0025] The mixtures of the invention may further comprise at least onewetting agent (D).

[0026] The amount of the oligomers and polymers (A) in the mixtures ofthe invention may vary very widely and is guided by the requirements ofthe respective end use. Preferably, the mixtures of the inventioncontain the oligomers and polymers (A) in an amount, based in each caseon the solids of the mixture of the invention, of from 10 to 98, morepreferably from 12 to 95, with particular preference from 14 to 92, withvery particular preference from 16 to 90, and in particular from 18 to88% by weight.

[0027] Here and below, solids means the sum of the constituents of therespective mixture of the invention which, following the heat cure,constitute the coatings, adhesive films or seals.

[0028] The amount of the thixotropic agents (B) in the mixtures of theinvention may also vary very widely. It, too, is guided by therequirements of the respective end use. Preferably, the mixtures of theinvention contain the thixotropic agents (B) in an amount, based in eachcase on the solids of the mixture of the invention, of from 0.1 to 5,more preferably from 0.2 to 4.5, with particular preference from 0.3 to4, with very particular preference from 0.4 to 3.5, and in particularfrom 0.5 to 3% by weight.

[0029] The mixtures of the invention contain the thixotropic agents (C),when used, in an amount, based in each case on the mixture of theinvention, of from 0.1 to 10, more preferably from 0.2 to 9, withparticular preference from 0.3 to 8, with very particular preferencefrom 0.4 to 7, and in particular from 0.5 to 6% by weight.

[0030] When used, the wetting agents (D) are present in the mixtures ofthe invention preferably in an amount, based in each case on the solidsof the mixture of the invention, of from 0.01 to 5, more preferably from0.02 to 4, with particular preference from 0.03 to 3, with veryparticular preference from 0.04 to 2, and in particular from 0.05 to 1%by weight.

[0031] Suitable oligomers and polymers (A) come from the polymer classesof the random, alternating and/or block, linear and/or branched and/orcomb, addition (co)polymers of ethylenically unsaturated monomers, orpolyaddition resins and/or polycondensation resins. For further detailsof these terms, refer to Römpp Lexikon Lacke und Druckfarben, GeorgThieme Verlag, Stuttgart, New York, 1998, page 457, “Polyaddition” and“Polyaddition resins (polyadducts)”, and also pages 463 and 464,“Polycondensates”, “Polycondensation” and “Polycondensation resins”.

[0032] Examples of highly suitable addition (co)polymers (A) are(meth)acrylate copolymers and partially saponified polyvinyl esters,especially (meth)acrylate copolymers.

[0033] Examples of highly suitable polyaddition resins and/orpolycondensation resins (A) are polyesters, alkyds, polyurethanes,polylactones, polycarbonates, polyethers, epoxy resin-amine adducts,polyureas, polyamides or polyimides.

[0034] With very particular preference, the oligomers and/or polymers(A) come from the polymer classes of the (meth)acrylate copolymers.

[0035] Oligomers and polymers (A) that contain allophanate groups andcome from the above-mentioned polymer classes are known from the Germanpatent application DE 198 39 453 A1, page 2 line 65 to page 6 line 34,and page 7 lines 25 to 53.

[0036] Oligomers and polymers (A) that contain carbamate groups and comefrom the above-mentioned polymer classes, and processes for preparingthem, are known from the patent applications

[0037] EP 0 594 068 A1, page 2 line 45 to page 4 line 27, page 5 lines36 to 57, and page 7 lines 1 to 22,

[0038] EP 0 594 142 A1, page 3 line 1 to page 4 line 37, page 5 line 49to page 6 line 12, and page 7 lines 5 to 26,

[0039] EP 0 675 141 B1, page 2 line 44 to page 5 line 15, page 8 line 5to page 10 line 41,

[0040] WO 94/10211, page 4 line 18 to page 8 line 8, page 12 line 30 topage 14 line 36, page 15 line 35 to page 17 line 32, and page 18 line 16to page 19 line 30, and

[0041] DE 199 46 048 A1.

[0042] The oligomers and/or polymers (A) are preferably prepared bycopolymerizing a monomer mixture containing at least one olefinicallyunsaturated carboxylic acid, methacrylic acid for example, in thepresence of a glycidyl ester of Versatic® acid (cf. Römpp Lexikon Lackeund Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998,“Versatic® acids”, pages 605 and 606) and then reacting the resultanthydroxyl-containing (meth)acrylate copolymer with at least onealkylurethane. Or else hydroxyl-containing (meth)acrylate copolymers areconverted using phosgene into (meth)acrylate copolymers containingchloroformate groups, after which the chloroformate groups are convertedinto carbamate groups using ammonia or primary amines.

[0043] Preferably, the oligomers and polymers (A) have a number-averagemolecular weight of from 600 to 20 000, more preferably from 800 to 15000, with particular preference from 1 000 to 10 000, with veryparticular preference from 1 200 to 8 000 and in particular from 1 200to 6 000 daltons.

[0044] The oligomers and polymers (A) may be rendered soluble in wateror dispersible in water through the incorporation of dispersing groups.Examples of suitable dispersing groups are anion-forming groups, such ascarboxylic acid, sulfonic acid or phosphonic acid groups, or anionicgroups, such as carboxylate, sulfonate or phosphonate groups,cation-forming groups, such as primary, secondary or tertiary aminogroups, or cationic groups, examples being ammonium groups, such asprimary, secondary, tertiary or quaternary ammonium groups, sulfoniumgroups and phosphonium groups, or polyalkylene oxide groups, such aspolyethylene oxide groups, which may be incorporated laterally,terminally and/or chain-internally into the oligomers and polymers (A)(cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag,Stuttgart, New York, 1998, “Water-dispersible binders”, page 619, and“Water-soluble binders” pages 626 and 625).

[0045] The thixotropic agents (B) are selected from the group consistingof urea derivatives preparable by reacting at least one amine and/orwater with at least one isocyanate in the presence of at least one aminoresin. For their preparation, it is preferred to use the amines.

[0046] The amines are preferably selected from the group consisting ofacyclic aliphatic, aliphatic-aromatic, cycloaliphatic,aliphatic-cycloaliphatic and cycloaliphatic-aromatic primary andsecondary monoamines and polyamines.

[0047] Examples of suitable monoamines are known from the patentapplications and patents cited at the outset, in particular from theGerman patent applications DE 199 24 172 A1, page 3 lines 3 to 10, or DE199 24 171 A1, page 3 lines 35 to 42, or from the international patentapplications WO 00/31194, page 11 lines 14 to 29, and WO 00/37520, page3 line 15 to page 4 line 5. Particular preference is given to usingmethoxypropylamine, benzylamine and/or n-hexylamine.

[0048] The polyamines contain on average per molecule at least twoprimary and/or secondary amino groups. Examples of suitable polyaminesare known from the international patent application WO 00/37520, page 4lines 6 to 19.

[0049] Suitable isocyanates include monoisocyanates and polyisocyanates.The monoisocyanates are used for the reaction with the polyamines andthe polyisocyanates for the reaction with the monoamines. Preferably,the polyisocyanates and the monoamines are used to prepare thethixotropic agents (B).

[0050] Examples of suitable monoisocyanates are known from theinternational patent application WO 00/37520, page 4 line 21 to page 5line 2.

[0051] It is preferred to use polyisocyanates containing on average permolecule at least 1.8, preferably at least 2, and in particular 2isocyanate groups. Examples of suitable polyisocyanates anddiisocyanates are described in detail in the international patentapplications WO 00/31194, page 11 line 30 to page 12 line 26, and WO00/37520, page 5 line 4 to page 6 line 27, or in German patentapplications DE 199 24 172 A1, page 3 lines 11 to 23, DE 199 24 170 A1,column 3 line 61 to column 6 line 68, or DE 199 24 171 A1, page 3 line43 to page 5 line 34. Particular preference is given to usinghexamethylene diisocyanate and/or its oligomers, especially trimers.

[0052] Suitable amino resins include in principle allformaldehyde-containing resins, as commonly used as crosslinking agentsin the field of coating materials, adhesives and sealing compounds. Itis preferred to use melamine resins.

[0053] Examples of suitable amino resins are described in Römpp LexikonLacke und Druckfarben, Georg Thieme Verlag, 1998, page 29, “Aminoresins”, in the textbook “Lackadditive” [Additives for coatings] byJohan Bieleman, Wiley-VCH, Weinheim, N.Y., 1998, pages 242 ff., in thebook “Paints, Coatings and Solvents”, second, completely revisededition, edited by D. Stoye and W. Freitag, Wiley-VCH, Weinheim, N.Y.,1998, pages 80 ff., in the American patent U.S. Pat. No. 4,710,542 A orpatent applications EP 0 245 700 A1 or WO 00/37520, page 3 lines 1 to13, and in the article by B. Singh and coworkers, “CarbamylmethylatedMelamines, Novel Crosslinkers for the Coatings Industry”, in AdvancedOrganic Coatings Science and Technology Series, 1991, Volume 13, pages193 to 207.

[0054] The reaction of the amines or of water, especially the amines,with the isocyanates has no special features in terms of its method butinstead takes place as described in the international patent applicationWO 00/37520, page 6 line 29 to page 8 line 14, and page 9 line 28 topage 10 line 32. For the preparation of the urea derivatives (B) on thetonne scale, the process known from the German patent application DE 19903 283 A1, in which an inline dissolver is used as the mixing unit, isadvantageous. In this case the weight ratio of amino resin tothixotropic agent (B) may be 100:1, preferqably 90:1, more preferably80:1, with particular preference 70:1, with very particular preference60:1, and in particular 50:1.

[0055] Amino resins containing thixotropic agents (B) prepared in thisway are customary and known and are sold, for example, under the brandname Setamine® XL 1268 by Akzo Nobel.

[0056] The silicas used as thixotropic agents (C) are selected from thegroup consisting of modified pyrogenic, hydrophilic and hydrophobic,transparent silicas. Particular preference is given to using hydrophobicpyrogenic silicon dioxides whose agglomerates and aggregates have achainlike structure and which may be prepared by flame hydrolysis ofsilicon tetrachloride in an oxyhydrogen flame. They are sold, forexample, by Degussa under the brand name Aerosil®. Particular preferenceis also given to using precipitated waterglasses, such asnanohectorites, which are sold, for example, by Südchemie under thebrand name Optigel® or by Laporte under the brand name Laponite®.Further examples of suitable silicas are those known from the Germanpatent application DE 199 24 172 A1, page 3 lines 28 to 32.

[0057] The wetting agents (D) are selected from the group consisting ofsiloxanes, fluorine compounds, carboxylic half-esters, phosphates,polyacrylic acids and their copolymers, and polyurethanes. It ispreferred to use polyurethanes. Particular advantages are possessed bythe wetting agents (D) described in the German patent application DE 19924 171 A1 from page 2 line 63 to page 3 line 24. Further highly suitablewetting agents are sold under the commercial designations Disperbyk® 361by Byk, Borchigen® by Bayer AG, and Tego Disperse® 710 by Tego ChemieServices.

[0058] The mixtures of the invention may comprise at least onecrosslinking agent containing on average per molecule at least tworeactive functional groups which are complementary to carbamate groupsand allophanate groups. In that case, the mixtures of the invention inquestion are externally crosslinking.

[0059] Alternatively to the crosslinking agents or additionally to them,it is possible to use oligomers and polymers (A) containing on averageper molecule at least one, in particular at least two, reactivefunctional groups which are complementary to carbamate groups andallophanate groups. In that case, the mixtures of the invention inquestion are partially or fully self-crosslinking.

[0060] Examples of suitable complementary reactive functional groups areN-methylol groups and N-methylol ether groups, preferably the methyl,ethyl, n-propyl and/or n-butyl ethers.

[0061] Furthermore, the oligomers and polymers (A) may contain furtherreactive functional groups which are able to undergo crosslinkingreactions with complementary reactive functional groups other than thosementioned above. Examples of suitable reactive functional groups areisocyanate-reactive functional groups, such as thiol, hydroxyl and/orprimary and/or secondary amino groups, especially hydroxyl groups, orepoxide-reactive groups such as the amino groups or carboxyl groups. Itis preferred to use hydroxyl groups.

[0062] The amount of the further reactive functional groups in theoligomers and/or polymers (A) may vary very widely. Preferably, theirhydroxyl number is from 20 to 120, more preferably from 25 to 110, withparticular preference from 30 to 100, with very particular preferencefrom 35 to 90, and in particular from 40 to 80 mg KOH/g. The acid numberor amine number is preferably from 5 to 100, more preferably from 10 to95, with particular preference from 15 to 90, with very particularpreference from 20 to 85, and in particular from 25 to 80 mg KOH/g.

[0063] Accordingly, the crosslinking agents comprise the above-describedamino resins, especially melamine resins. Preferably they are used inthe mixtures of the invention in the amounts specified in the Germanpatent DE 199 24 171 A1 on page 8 lines 48 to 57, the amount introducedby means of the above-described mixtures of amino resins and thixotropicagents (B) being included in the calculation.

[0064] In addition to the above-described crosslinking agents it ispossible to use further crosslinking agents, especially if the oligomersand/or polymers also contain the above-described further reactivefunctional groups. Examples of suitable further crosslinking agents areknown from the German patent applications DE 199 24 171 A1, page 7 line38 to page 8 line 35 and page 8 lines 43 to 47, or DE 199 24 172 A1,page 5 line 22 to page 6 line 50 and page 6 lines 58 to 61. Inparticular, use is made of the blocked, part-blocked and unblockedpolyisocyanates described therein. Accordingly, the mixtures of theinvention may comprise one- or two-component or multicomponent systems.

[0065] The crosslinking agents are preferably present in total in themixtures of the invention in an amount, based on the mixture of theinvention, of from 5 to 70, more preferably from 10 to 65, withparticular preference from 15 to 60, with very particular preferencefrom 20 to 55, and in particular from 20 to 50% by weight. In thiscontext it is further advisable to choose the amounts of crosslinkingagents and oligomers and/or polymers (A) such that in the mixtures ofthe invention the ratio of reactive functional groups in thecrosslinking agent and complementary reactive functional groups in theoligomers and/or polymers (A) is from 2:1 to 1:2, preferably from 1.5:1to 1:1.5, with particular preference from 1.2:1 to 1:1.2, and inparticular from 1.1:1 to 1:1.1. Furthermore, it is of advantage if theadditional crosslinking agent is employed in smaller amounts than thecrosslinking agent. Preferably, the proportion of crosslinking agent toadditional crosslinking agent is 10:1, more preferably 8:1, withparticular preference 6:1, with very particular preference 5:1, and inparticular 4:1.

[0066] Apart from the constituents (A) and (B) and also, whereappropriate, (C), (D) and crosslinking agents described above, themixture of the invention may further comprise at least one additive.

[0067] In the case of pigmented mixtures of the invention, said mixturescomprise pigments and fillers selected from the group consisting ofcustomary and known organic and inorganic, color and/or effect,electrically conductive, magnetically shielding and fluorescent pigmentsand customary and known organic and inorganic fillers other than thethixotropic agents (C).

[0068] These pigments and fillers are used if the mixtures of theinvention are used as pigmented adhesives and sealing compounds and alsocoating materials, such as primer-surfacers, basecoat materials orsolid-color topcoat materials.

[0069] Additives which may be used both in the pigmented and in theunpigmented mixtures of the invention are known from the German patentapplications DE 199 24 170 A1, column 13 line 6 to column 14 line 2, DE199 24 171 A1, page 8 line 65 to page 9 line 33, or DE 198 39 453 A1,page 6 line 68 to page 7 line 6, with the exception here of the wettingagents (D) and the transparent fillers based on silicon dioxide.

[0070] Further examples of suitable additives are oligomers and/orpolymers which are free from carbamate and/or allophanate groups, whichcome from the above-described polymer classes, especially the class of(meth)acrylate copolymers, and which contain the above-describedadditional reactive functional groups, especially hydroxyl groups.Suitable oligomers or polymers are described in detail in the patentapplications mentioned above relating to the oligomers and polymers (A)or in the German patent application DE 139 08 018 A1, page 9 line 31 topage 11 line 37. Particularly advantageous are the (meth)acrylatecopolymers which contain in copolymerized form alkyl (meth)acrylatesselected from the group consisting of 2- and 3-propyl (meth)acrylate and3- and 4-n-butyl (meth)acrylate.

[0071] The preparation of the mixtures of the invention has no specialfeatures in terms of its method but instead takes place by the mixing ofthe above-described constituents (A) and (B) or (A), (B) and (C) and/or(D) and also, if desired, of the above-described crosslinking agentsand/or additives. This may be done using mixing units such as stirredtanks, dissolvers, inline dissolvers, stirred mills, static mixers,toothed-wheel dispersers or extruders.

[0072] Depending on their end use, the mixtures of the invention may bepresent in organic solvents as solutions and/or dispersions (nonaqueousdispersions, NADs) or as substantially or entirely solvent-freemixtures. The substantially or entirely solvent-free mixtures may bepresent in liquid form (100% system) or powder form. Furthermore, themixtures of the invention may be present in solution or dispersion inwater. Not least, the pulverulent mixtures of the invention may bepresent in the form of dispersions in water, as what are known as powderslurries. Preferably, the mixtures of the invention are present indispersion and/or solution in organic solvents.

[0073] The mixtures of the invention are outstandingly suitable ascoating materials, adhesives and sealing compounds, or for preparingthem. The coating materials of the invention are outstandingly suitablefor the production of single-coat or multicoat, color and/or effect,electrically conductive, magnetically shielding or fluorescent coatings,such as primer-surfacer coats, basecoats or solid-color topcoats, or ofsingle-coat or multicoat clearcoat systems. The adhesives of theinvention are outstandingly suitable for the production of adhesivefilms, and the sealing compounds of the invention are outstandinglysuitable for the production of seals.

[0074] Very particular advantages result when the mixtures of theinvention are used as clearcoat materials to produce single-coat ormulticoat clearcoat systems. In particular, the clearcoat materials ofthe invention are used to produce multicoat color and/or effect coatingsystems by the wet-on-wet technique, in which a basecoat material,especially an aqueous basecoat material, is applied to the surface of asubstrate, after which the resultant basecoat film is dried, withoutbeing cured, and is overcoated with a clearcoat film. Subsequently, thetwo films are cured together.

[0075] In terms of its method, the application of the coating materials,adhesives and sealing compounds of the invention has no special featuresbut may instead take place by any customary application method, such asspraying, knifecoating, brushing, flowcoating, dipping, trickling, orrolling, for example. In the context of the coating materials of theinvention it is preferred to employ spray application methods, such ascompressed air spraying, airless spraying, high-speed rotation,electrostatic spray application (ESTA), for example, alone or inconjunction with hot spray application such as hot air spraying, forexample.

[0076] Suitable substrates are all those whose surface is undamaged bythe application of heat in the course of the curing of the films presentthereon. The substrates preferably consist of metals, plastics, wood,ceramic, stone, textile, fiber composites, leather, glass, glass fibers,glass wool, rockwool, mineral- and resin-bound building materials, suchas plasterboard and cement slabs or roof tiles, and also composites ofthese materials.

[0077] Accordingly, the coating materials, adhesives and sealingcompounds of the invention are suitable not only for applications in thefields of automotive OEM finishing and automotive refinish but are alsoappropriate for the coating, bonding and sealing of buildings, insideand out, and of doors, windows and furniture, for industrial coating,including coil coating, container coating and the impregnation and/orcoating of electrical components, and for the coating of white goods,including domestic appliances, boilers and radiators. In the context ofindustrial coatings, they are suitable for coating, bonding or sealingvirtually all parts and articles for private or industrial use, such asdomestic appliances, small metal parts such as nuts and bolts, hub caps,wheel rims, packaging, or electrical components, such as motor windingsor transformer windings.

[0078] In the case of electrically conductive substrates it is possibleto use primers which are produced in a customary and known manner fromelectrodeposition coating materials. For this purpose both anodic andcathodic electrodeposition coating materials are suitable, butespecially cathodic electrodeposition coating materials.Unfunctionalized and/or nonpolar plastics surfaces may be subjected,prior to coating in a known manner, to a pretreatment, such as with aplasma or by flaming, or may be provided with a water-based primer.

[0079] The curing of the applied mixtures of the invention also has nospecial features in terms of its method but instead takes place inaccordance with the customary and known thermal methods, such as heatingin a forced air oven or irradiation using IR lamps.

[0080] The resultant coatings of the invention, especially thesingle-coat or multicoat color and/or effect coating systems andclearcoats of the invention, are easy to produce and exhibit outstandingoptical properties and very high light stability, chemical resistance,water resistance, condensation resistance, and weathering stability. Inparticular, they are free from turbidities and inhomogeneities.Moreover, they are hard, flexible and scratch-resistant. They exhibitvery good reflow characteristics, outstanding intercoat adhesion betweenbasecoat and clearcoat, and good to very good adhesion to customary andknown automotive refinishes.

[0081] The adhesive films of the invention permanently and firmly join avery wide variety of substrates to one another and possess high chemicaland mechanical stability even in the case of extreme temperatures and/ortemperature fluctuations.

[0082] Similarly, the seals of the invention seal the substratespermanently, and exhibit high chemical and mechanical stability even inthe case of extreme temperatures and/or temperature fluctuations andeven in conjunction with exposure to aggressive chemicals.

[0083] In particular, however, the coatings of the invention possess ahigh stonechip resistance, and so may be used with particular advantagein the field of automotive coatings.

[0084] Accordingly, the primed or unprimed substrates commonly employedin the technological fields recited above and coated with at least onecoating of the invention, bonded with at least one adhesive film of theinvention and/or sealed with at least one seal of the invention combinea particularly advantageous profile of performance properties with aparticularly long service life, so making them particularly attractiveeconomically.

EXAMPLES Preparation Example 1

[0085] The Preparation of a Methacrylate Copolymer Containing HydroxylGroups

[0086] A 4-liter reactor equipped with a stirrer, two dropping funnelsas feeds for the monomer mixture and the initiator solution, a nitrogeninlet pipe, a thermometer and a reflux condenser was charged with 731parts by weight of an aromatic hydrocarbons fraction having a boilingrange of from 158 to 172° C. and this initial charge was heated to 140°C. Thereafter a monomer mixture of 183 parts by weight of n-butylmethacrylate, 458 parts by weight of ethylhexyl methacrylate, 214 partsby weight of styrene, 183 parts by weight of hydroxyethyl acrylate, 458parts by weight of 4-hydroxybutyl acrylate and 31 parts by weight ofacrylic acid was metered into the reactor at a uniform rate over thecourse of four hours and an initiator solution of 153 parts by weight oftert-butyl perethylhexanoate in 92 parts by weight of theabove-described aromatic solvent was metered into the reactor at auniform rate over the course of 4.5 hours. The addition of the monomermixture and of the initiator solution was commenced simultaneously.After the end of the addition of the initiator, the reaction mixture washeated at 140° C. with stirring for 2 hours more and then cooled. Theresultant resin solution had a solids content of 65% (forced air oven;one hour; 130° C.).

Preparation Example 2

[0087] The Preparation of a Methacrylate Copolymer ContainingChloroformate Groups

[0088] 700 parts by weight of the resin solution from preparationexample 1 were diluted with 700 parts by weight of xylene in order toimprove their stirrability. The resultant mixture was introduced into anappropriate reactor. Subsequently, over the course of one hour, 400parts by weight of phosgene were added to the resin solution at roomtemperature and with stirring. After a subsequent reaction period of 30minutes, the degree of conversion was determined by means of IRspectroscopy. When this was done, hydroxyl groups were no longerdetectable. The excess phosgene was separated off under reducedpressure. From the determination of the chlorine value, aconversion >90% was found.

Preparation Example 3

[0089] The Preparation of the Methacrylate Copolymer (A) ContainingCarbamate Groups

[0090] 1450 parts by weight of the resin solution containingchloroformate groups from preparation example 2 were introduced into anappropriate reactor. Subsequently, 61 parts by weight of ammonia wereintroduced at room temperature into the resin solution, with ammoniumchloride being precipitated.

[0091] The resultant resin solution was admixed in succession with 500parts by weight of water, 400 parts by weight of ethanol and 500 partsby weight of pentyl acetate in order to dissolve the precipitatedammonium chloride and to bring about phase separation. The resultantmixture was stirred at room temperature for one hour and then left tostand in order for phase separation to take place. After it had takenplace, the aqueous phase was separated off and the organic phase wasdried with sodium chloride.

[0092] NMR analysis revealed that more than 80% of the chloroformategroups had been converted into carbamate groups. The resultant solutionof the methacrylate copolymer (A) had a solids content of 68.6% byweight (forced air oven; one hour; 30° C.), a viscosity of 8.4 dPas(original), and a viscosity of 5.6 dPas in 65% dilution in solventnaphtha.

Example 1

[0093] The Preparation of an Inventive Clearcoat Material

[0094] The inventive clearcoat material was prepared by mixing andhomogenizing the following constituents:

[0095] 222 parts by weight of the methacrylate copolymer solution (A)from preparation example 3,

[0096] 42.2 parts by weight of Setamine® XL 1268 [urea-modified melamineresin (Resimene® 755 from Monsanto, 80 percent strength in isobutanol)from Akzo Nobel; amount of thixotropic agent (B) present: 2.4% byweight],

[0097] 5.2 parts by weight of Tinuvin® 384 (commercial UV absorber fromCiba Specialty Chemicals, Inc.),

[0098] 2.6 parts by weight of Tinuvin® 123 (commercial reversiblefree-radical scavenger, sterically hindered amine (HALS) from CibaSpecialty Chemicals, Inc.),

[0099] 6.8 parts by weight of Nacure® 5528 (commercial catalyst(amine-blocked sulfonic acid derivative) from King),

[0100] 6.0 parts by weight of a five percent strength solution of acommercial leveling agent based on polydimethylsiloxane in xylene,

[0101] 0.8 part by weight of Byk® 306 (commercial additive from BykChemie),

[0102] 31 parts by weight of ethylhexanol,

[0103] 15 parts by weight of n-butanol,

[0104] 3 parts by weight of pine oil, 85 percent, and

[0105] 20 parts by weight of butyl diglycol.

[0106] Using the mixture of the above-mentioned solvents, the clearcoatmaterial was adjusted to a viscosity of 25 seconds in the DIN 4 flowcup. It then had a solids content of 45.5% by weight (one hour forcedair oven/130° C.).

Example 2

[0107] The Production of an Inventive Multicoat Color Coating System

[0108] To produce the multicoat system, steel test panels coated with anelectrodeposition coating in a dry film thickness of from 18 to 22 μmwere coated with a waterborne primer-surfacer. The resultant waterborneprimer-surfacer film was baked at 160° C. for 20 minutes to give aprimer-surfacer coat with a dry film thickness of from 35 to 40 μm. Theprimer-surfacer coat was subsequently coated with a black aqueousbasecoat material from BASF Coatings AG in a film thickness of from 12to 15 μm. The resultant aqueous basecoat films were flashed off at 80°C. for 10 minutes. Thereafter, the clearcoat material from example 1 wasapplied pneumatically using a gravity-feed gun in one cross-pass in afilm thickness of from 40 to 45 μm. Subsequently, the clearcoat filmswere flashed off at room temperature for 10 minutes and at 80° C. for 10minutes and together with the aqueous basecoat films were baked in aforced air oven at a panel temperature of 130° C. for 25 minutes.

[0109] For the wetting test, relatively thin clearcoat films wereapplied and baked in the manner described above. The test revealed thatvery good wetting was present even with a film thickness below 20 μm.

[0110] For the leveling test, the clearcoat material waselectrostatically applied vertically and horizontally to the testpanels. This was done using an Eco-bell with direct charging. Theleveling was assessed visually as being particularly good (very smoothsurface). This is underscored by the measurement of the wave-scanvalues, which is familiar to the skilled worker:

[0111] longwave/shortwave at 40 μm, horizontal application: 8.2/3.9

[0112] longwave/shortwave at 40 μm, vertical application: 12.1/5.1.

[0113] (Instrument: Byk/Gardner—wave-scan plus).

[0114] In order to test for the tendency to run, customary and knownperforated metal sheets with diagonal rows of holes were used instead ofthe test panels. The clearcoat material was applied electrostatically ina film thickness of <20 μm to 65 μm. This was done using an Eco-bellwith direct charging. Basecoat and clearcoat were baked in verticalposition. Initial signs of runs occurred only at clearcoatthicknesses >50 μm; the runs reached a length of 1 cm only at 55 μm.

[0115] The resultant multicoat system was highly brilliant and had agloss (200) to DIN 67530 of 91.

[0116] The scratch resistance was assessed with the aid of the sand test(cf. the German patent application DE 198 39 453 A1, page 9 lines 1 to63) using the metal test panels described above. Following damage atroom temperature a loss of gloss by only 13.5 units (200) to 77.5 wasfound, which underlined the high scratch resistance. The gloss roseafter 2 hours at 40° C. to 78.2 and after 2 hours at 60° C. to 80.6,which demonstrated the very good reflow characteristics.

[0117] Furthermore, the scratch resistance was assessed with the aid ofa brush test (cf. the German patent application DE 198 39 453 A1, page 9lines 17 to 63) using the metal test panels described above. Followingdamage, a loss of gloss by only 8.8 units (200) to 82.2 was found, whichunderlines the high scratch resistance. The gloss rose after 2 hours at40° C. to 85.9 and after 2 hours at 60° C. to 89, which underlines thevery good reflow characteristics.

[0118] The chemical resistance was determined in accordance with BART.

[0119] The BART (BASF acid resistance test) was used to determine theresistance of film surfaces to acids, alkalis and water drops. Afterbaking, the coating was exposed to further temperature loads in agradient oven (30 min at 40° C., 50° C., 60° C., and 70° C.). Beforehandthe test substances (1%, 10%, and 36% sulfuric acid; 5% sulfurous acid,10% hydrochloric acid, 5% sodium hydroxide solution, DI (i.e.,deionized) water (1, 2, 3 or 4 drops) have been applied in a definedmanner using a volumetric pipette. Following exposure to the substances,they were removed under running water and the damage was assessedvisually after 24 h in accordance with a specified scale: RatingAppearance 0 no defect 1 slight marking 2 marking/matting/no softening 3marking/matting/color change/softening 4 cracks/incipient etching 5clearcoat removed

[0120] Each individual mark (spot) was evaluated and the result wasnoted for each coating in appropriate form (e.g., rating totals for onetemperature).

[0121] The results of the test can be found in the table.

[0122] The BART underscores the extraordinary acid resistance of themulticoat system of the invention and of the clearcoat material of theinvention. TABLE The acid resistance of the multicoat system of theinvention, ML, in accordance with BART Test substance 40° C. 50° C. 60°C. 70° C.  1% sulfuric acid 0 0 0 1 10% sulfuric acid 0 0 0 2 36%sulfuric acid 0 0 0.5 3 10% hydrochloric acid 0 0 0 0  5% sulfurous acid0 0 0 1  5% sodium hydroxide solution 0 0 0 0 DI water 1 0 0 0 0 DIwater 2 0 0 0 0 DI water 3 0 0 0 0 DI water 4 0 0 0 0 Total 0 0 0.5 7

What is claimed is:
 1. A heat-curable thixotropic mixture containingcarbamate and/or allophanate groups, comprising (A) at least oneoligomer and/or polymer selected from the group consisting of oligomersand polymers containing allophanate groups, carbamate groups, andcarbamate and allophanate groups, and (B) at least one thixotropic agentselected from the group consisting of urea derivatives preparable byreacting at least one amine and/or water with at least one isocyanate inthe presence of at least one amino acid.
 2. The mixture as claimed inclaim 1, wherein the urea derivatives (B) are preparable by reacting atleast one monoamine with at least one polyisocyanate or by reacting atleast one polyamine with at least one monoisocyanate.
 3. The mixture asclaimed in claim 1 or 2, wherein the amines are selected from the groupconsisting of acyclic aliphatic, aliphatic-aromatic, cycloaliphatic,aliphatic-cycloaliphatic, and cycloaliphatic-aromatic, primary andsecondary monoamines and polyamines.
 4. The mixture as claimed in claim3, wherein the amines are selected from the group of the monoamines. 5.The mixture as claimed in any of claims 1 to 5, wherein thepolyisocyanates contain on average per molecule at least 1.8 isocyanategroups.
 6. The mixture as claimed in any of claims 1 to 5, comprising atleast one silica as thixotropic agent (C).
 7. The mixture as claimed inany of claims 1 to 6, comprising at least one wetting agent (D).
 8. Themixture as claimed in any of claims 1 to 7, wherein the oligomers andpolymers (A) are selected from the group consisting of random,alternating and block, linear and branched and comb addition(co)polymers of ethylenically unsaturated monomers, and polyadditionresins and polycondensation resins.
 9. The mixture as claimed in claim8, wherein the addition (co)polymers (A) are selected from the groupconsisting of (meth)acrylate copolymers and polyvinyl esters and thepolyaddition resins and polycondensation resins are selected from thegroup consisting of polyesters, alkyds, polyurethanes, polylactones,polycarbonates, polyethers, epoxy resin-amine adducts, polyureas,polyamides and polyimides.
 10. The mixture as claimed in any of claims 6to 9, wherein the silicas (C) are selected from the group consisting ofmodified pyrogenic, hydrophilic and hydrophobic, transparent silicas.11. The mixture as claimed in any of claims 7 to 10, wherein the wettingagents are selected from the group consisting of siloxanes, fluorinecompounds, carboxylic half-esters, phosphates, polyacrylic acids andtheir copolymers, and polyurethanes.
 12. The mixture as claimed in anyof claims 1 to 11, comprising at least one crosslinking agent containingon average per molecule at least two reactive functional groups whichare complementary to carbamate groups and allophanate groups.
 13. Themixture as claimed in any of claims 1 to 12, wherein the oligomers andpolymers (A) contain on average per molecule at least one reactivefunctional group which is complementary to carbamate groups andallophanate groups.
 14. The mixture as claimed in claim 12 or 13,wherein the complementary reactive functional groups are selected fromthe group consisting of N-methylol groups and N-methylol ether groups.15. A process for preparing a heat-curable thixotropic mixturecontaining carbamate and/or allophanate groups as claimed in any ofclaims 1 to 14 by mixing of the constituents (A) and (B) and, whereappropriate, (C), (D), at least one crosslinking agent and/or at leastone additive, which comprises preparing the thixotropic agent (B) byreacting at least one amine and/or water with at least onepolyisocyanate or by reacting at least one polyamine with at least onemonoisocyanate in the presence of at least one amino resin.
 16. The useof the heat-curable thixotropic mixture containing carbamate and/orallophanate groups as claimed in any of claims 1 to 14 as a coatingmaterial, adhesive or sealing compound.
 17. The use as claimed in claim16, wherein the coating material is used as a clearcoat material. 18.The use as claimed in claim 16 or 17, wherein the coating material,adhesive or sealing compound is used in the fields of automotive OEMfinishing, automotive refinish, the coating of buildings, inside andout, the coating of furniture, windows and doors, and industrialcoating, including coil coating, container coating, the impregnation orcoating of electrical components and the coating of white goods,including domestic appliances, boilers and radiators.